Strain-Driven Superlubricity of Graphene/Graphene in Commensurate Contact

The occurrence of structural superlubricity (SSL) requires that two sliding surfaces be in incommensurate contact. However, the incommensurate contact between two sliding surfaces is fundamentally an instable state whose maintenance over time is extremely laborious. To circumvent this difficulty, it is proposed in the present work to change the paradigm of making appear superlubricity and keeping it over time. Two graphene layers in sliding commensurate contact, which are subjected to an isotropic in-plane synchronous strain, are considered and studied. First, by DFT calculations, it is demonstrated that the synchronous strain-driven superlubricity (SSDSL) takes place for some particular sliding paths or for all sliding paths, once the compressive strain prescribed reaches 15% or 35%. Next, the Prandtl-Tomlinson (P-T) model is used to explain how to modulate stick-slip, continuous and frictionless slides by the strain. Finally, the SSDSL of two graphene layers in commensurate contact is justified in detail by the interfacial charge density transfer due to the strain. The results obtained by the present work open a new perspective of realizing superlubricity in a robust way.

Automated summary

The occurrence of structural superlubricity (SSL) requires incommensurate contact between two sliding surfaces, which is unstable to maintain over time. This study proposes a paradigm shift in achieving and maintaining superlubricity by considering two graphene layers in sliding commensurate contact subjected to isotropic in-plane synchronous strain. DFT calculations demonstrate that synchronous strain-driven superlubricity (SSDSL) occurs for specific or all sliding paths when the prescribed compressive strain reaches 15% or 35%. The Prandtl-Tomlinson (P-T) model explains how stick-slip, continuous, and frictionless slides can be modulated by strain. The detailed justification of SSDSL in commensurate contact of graphene layers is attributed to interfacial charge density transfer due to strain. This work presents a new perspective on achieving robust superlubricity.